text: /*
   * RTP AMR Depacketizer, RFC 3267
   * Copyright (c) 2010 Martin Storsjo
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include "libavutil/channel_layout.h"
  #include "avformat.h"
  #include "rtpdec_formats.h"
  #include "libavutil/avstring.h"
  
  static const uint8_t frame_sizes_nb[16] = {
      12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0, 0, 0
  };
  static const uint8_t frame_sizes_wb[16] = {
      17, 23, 32, 36, 40, 46, 50, 58, 60, 5, 5, 0, 0, 0, 0, 0
  };
  
  struct PayloadContext {
      int octet_align;
      int crc;
      int interleaving;
      int channels;
  };
  
  static av_cold int amr_init(AVFormatContext *s, int st_index, PayloadContext *data)
  {
      data->channels = 1;
      return 0;
  }
  
  static int amr_handle_packet(AVFormatContext *ctx, PayloadContext *data,
                               AVStream *st, AVPacket *pkt, uint32_t *timestamp,
                               const uint8_t *buf, int len, uint16_t seq,
                               int flags)
  {
      const uint8_t *frame_sizes = NULL;
      int frames;
      int i;
      const uint8_t *speech_data;
      uint8_t *ptr;
  
      if (st->codecpar->codec_id == AV_CODEC_ID_AMR_NB) {
          frame_sizes = frame_sizes_nb;
      } else if (st->codecpar->codec_id == AV_CODEC_ID_AMR_WB) {
          frame_sizes = frame_sizes_wb;
      } else {
          av_log(ctx, AV_LOG_ERROR, "Bad codec ID\n");
          return AVERROR_INVALIDDATA;
      }
  
      if (st->codecpar->channels != 1) {
          av_log(ctx, AV_LOG_ERROR, "Only mono AMR is supported\n");
          return AVERROR_INVALIDDATA;
      }
      st->codecpar->channel_layout = AV_CH_LAYOUT_MONO;
  
      /* The AMR RTP packet consists of one header byte, followed
       * by one TOC byte for each AMR frame in the packet, followed
       * by the speech data for all the AMR frames.
       *
       * The header byte contains only a codec mode request, for
       * requesting what kind of AMR data the sender wants to
       * receive. Not used at the moment.
       */
  
      /* Count the number of frames in the packet. The highest bit
       * is set in a TOC byte if there are more frames following.
       */
      for (frames = 1; frames < len && (buf[frames] & 0x80); frames++) ;
  
      if (1 + frames >= len) {
          /* We hit the end of the packet while counting frames. */
          av_log(ctx, AV_LOG_ERROR, "No speech data found\n");
          return AVERROR_INVALIDDATA;
      }
  
      speech_data = buf + 1 + frames;
  
      /* Everything except the codec mode request byte should be output. */
      if (av_new_packet(pkt, len - 1)) {
          av_log(ctx, AV_LOG_ERROR, "Out of memory\n");
          return AVERROR(ENOMEM);
      }
      pkt->stream_index = st->index;
      ptr = pkt->data;
  
      for (i = 0; i < frames; i++) {
          uint8_t toc = buf[1 + i];
          int frame_size = frame_sizes[(toc >> 3) & 0x0f];
  
          if (speech_data + frame_size > buf + len) {
              /* Too little speech data */
              av_log(ctx, AV_LOG_WARNING, "Too little speech data in the RTP packet\n");
              /* Set the unwritten part of the packet to zero. */
              memset(ptr, 0, pkt->data + pkt->size - ptr);
              pkt->size = ptr - pkt->data;
              return 0;
          }
  
          /* Extract the AMR frame mode from the TOC byte */
          *ptr++ = toc & 0x7C;
  
          /* Copy the speech data */
          memcpy(ptr, speech_data, frame_size);
          speech_data += frame_size;
          ptr += frame_size;
      }
  
      if (speech_data < buf + len) {
          av_log(ctx, AV_LOG_WARNING, "Too much speech data in the RTP packet?\n");
          /* Set the unwritten part of the packet to zero. */
          memset(ptr, 0, pkt->data + pkt->size - ptr);
          pkt->size = ptr - pkt->data;
      }
  
      return 0;
  }
  
  static int amr_parse_fmtp(AVFormatContext *s,
                            AVStream *stream, PayloadContext *data,
                            const char *attr, const char *value)
  {
      /* Some AMR SDP configurations contain "octet-align", without
       * the trailing =1. Therefore, if the value is empty,
       * interpret it as "1".
       */
      if (!strcmp(value, "")) {
          av_log(s, AV_LOG_WARNING, "AMR fmtp attribute %s had "
                                    "nonstandard empty value\n", attr);
          value = "1";
      }
      if (!strcmp(attr, "octet-align"))
          data->octet_align = atoi(value);
      else if (!strcmp(attr, "crc"))
          data->crc = atoi(value);
      else if (!strcmp(attr, "interleaving"))
          data->interleaving = atoi(value);
      else if (!strcmp(attr, "channels"))
          data->channels = atoi(value);
      return 0;
  }
  
  static int amr_parse_sdp_line(AVFormatContext *s, int st_index,
                                PayloadContext *data, const char *line)
  {
      const char *p;
      int ret;
  
      if (st_index < 0)
          return 0;
  
      /* Parse an fmtp line this one:
       * a=fmtp:97 octet-align=1; interleaving=0
       * That is, a normal fmtp: line followed by semicolon & space
       * separated key/value pairs.
       */
      if (av_strstart(line, "fmtp:", &p)) {
          ret = ff_parse_fmtp(s, s->streams[st_index], data, p, amr_parse_fmtp);
          if (!data->octet_align || data->crc ||
              data->interleaving || data->channels != 1) {
              av_log(s, AV_LOG_ERROR, "Unsupported RTP/AMR configuration!\n");
              return -1;
          }
          return ret;
      }
      return 0;
  }
  
  const RTPDynamicProtocolHandler ff_amr_nb_dynamic_handler = {
      .enc_name         = "AMR",
      .codec_type       = AVMEDIA_TYPE_AUDIO,
      .codec_id         = AV_CODEC_ID_AMR_NB,
      .priv_data_size   = sizeof(PayloadContext),
      .init             = amr_init,
      .parse_sdp_a_line = amr_parse_sdp_line,
      .parse_packet     = amr_handle_packet,
  };
  
  const RTPDynamicProtocolHandler ff_amr_wb_dynamic_handler = {
      .enc_name         = "AMR-WB",
      .codec_type       = AVMEDIA_TYPE_AUDIO,
      .codec_id         = AV_CODEC_ID_AMR_WB,
      .priv_data_size   = sizeof(PayloadContext),
      .init             = amr_init,
      .parse_sdp_a_line = amr_parse_sdp_line,
      .parse_packet     = amr_handle_packet,
  };
  